1. Field of the Invention
The present disclosure relates to a technical field of display, more particularly, to a mask.
2. Description of the Related Art
In a technical field of display, a mask is served as a very important patterning tool in semiconductor display industry. The mask is used to transfer a mask pattern on the mask onto a target substrate in a ratio of 1:1, so that conductive patterns or slit patterns are formed onto the target substrate.
The mask includes a light shielding area and a light transmission area, and the light shielding area is provided with a plurality of light shielding layers in different regions for shielding lights. Typically, the light shielding layer is a conductive layer having a relatively good etching property, but it tends to accumulate electrical charges, thereby generating an undesirable phenomenon of electro-static discharge (abbreviated, ESD).
Reasons for electrical charges being accumulated onto the mask mainly include the following aspects: during carrying or cleaning the mask or the like, it is easy for the electrical charges to accumulate onto the mask due to frictional effects, thereby forming the static electricity. It would cause the undesirable phenomenon of ESD once the electrostatic charges are accumulated up to a certain quantity. Release of the electrostatic charges will breakdown the light shielding layer on the mask, and the preset mask pattern corresponding to the light shielding layer would be damaged. Once such mask goes into production, it would cause enormous economic loss.
In a process of manufacturing products in practice, or in a process of exposing with the mask, it is inevitable that foreign matters will fall onto the mask. In order to avoid defects that the foreign matters on the mask cause bad reproducibility of the products, it is common to clean the mask with clean dry air (abbreviated, CDA). During the cleaning operation of the mask, CDA gas flow will bring friction with the light shielding layer on the mask, thereby generating a certain quantity of electrostatic charges on the light shielding layer. Since the substrate is typically made of insulative glass, the electrostatic charges on the light shielding layer cannot be released in time by means of the substrate. Once the electrostatic charges are built up to a certain extent, the electrostatic charges will be conducted on the conductive light shielding layers, thereby ESD will be generated where the charges are accumulated to the certain extent. In this way, the pattern of the mask is damaged, thus resulting in the gigantic economic loss.
In addition, upon manually carrying the mask, it is also easy to accumulate charges on the mask due to the contact friction and generate electrostatic charges. Thus, the undesirable phenomenon of ESD would take place.
As shown in FIG. 1, the main structure of the mask includes a light transmittive substrate 1, and a light transmission area and a light shielding area on the substrate 1. The light shielding area is provided with at least two conductive light shielding layers having preset mask patterns. One example of the mask pattern of the light shielding area is shown as in FIG. 1. The light shielding area includes a first light shielding layer 11, a second light shielding layer 12, a third light shielding layer 13, a fourth light shielding layer 14, a fifth light shielding layer 15 and a sixth light shielding layer 16. Respective light shielding layers are separated from each other and insulated from each other. The first light shielding layer 11 is in a comb-like form, while the remaining light shielding layers are in a strip-like form respectively. The second to sixth light shielding layers 12-16 are spaced apart by the comb-like parts in the first light shielding layer 11. As shown by the area marked by the dash line in FIG. 1, the comb-like parts within the area marked by the dash line are relatively dense, and thus a relatively large number of charges are easy to accumulate here. The charges on the first to sixth light shielding layers 11-16 cannot be released rapidly, and thus may be accumulated onto some light shielding layer. Therefore, it is easy to generate the ESD phenomenon. During the release of the electrostatic charges, relatively larger current would breakdown the light shielding layer, and damage the mask pattern of the light shielding layer.